1. Field of the Invention
The present invention relates to a structure of touch display panel and, more particularly, to an in-cell OLED touch display panel structure.
2. Description of Related Art
Among many types of flat panel displays, the organic light emitting diode display (OLED) technology is the one with great potential. OLED was first published by Eastman Kodak Co. in 1987. It has the features of thinness, light weight, self-illumination, low driving voltage, high efficiency, high contrast, high color saturation, fast response, flexibility, etc., and is therefore deemed as positively evaluated display technology following the TFT-LCD.
In recent years, due to the development of mobile communications, digital products and digital televisions, the demand for high-quality full-color flat-panel displays is rapidly increased. The OLED display is provided with not only the advantages of LCD display including thinness, power-saving, and full-color display, but also the features of wide viewing angle, self-illumination, and fast response that are better than LCD.
FIG. 1 schematically illustrates the basic structure of prior OLED display. The OLED display 100 includes a cathode layer 110, an OLED layer 120, an anode layer 130, a thin film transistor layer 140, a lower substrate 150, and an upper substrate 160, wherein the OLED layer 120 further includes a hole transporting layer (HTL) 121, an emitting layer 123, and an electron transporting layer (ETL) 125.
The light-emitting principle of OLED is such that the electrons and electric holes are injected from the cathode layer 110 and the anode layer 130 respectively by applying electric field and, after the electric holes pass through the electric hole transport sub-layer 121 and electrons pass through the electron transport sub-layer 125, the electrons and electric holes enter the light-emitting layer 123 with fluorescent characteristics and then are combined to produce excited photons, which immediately release energy and return to the ground state. The released energy will generate different colors of light based on different luminescent materials, so as to cause OLED to emit light.
Full-color OLED display method can be divided into RGB pixels placement method, color conversion method, color filter method, micro resonant tone color method, multi-layer stacking method, and so on. The principle of the color filter method of OLED is the same with that of the full-color LCD display method, except that it just uses white OLED light and uses color filters to filter out red, blue, and green primary colors. Due to the use of a single OLED light source, the lifetime of the red, blue and green primary colors is the same and thus there is no color distortion phenomenon. Moreover, it can be combined with the mature color filter technology for mass production. Thus, many manufacturers adopt the color filter method as the method of full-color OLED display.
The conventional touch display panel includes a touch panel and a display unit overlapped with the touch panel. The touch panel is configured as an operation interface. The touch panel is transparent so that an image generated by the display unit can be viewed directly by a user without being sheltered by the touch panel. Such well known skill of the touch panel may increase additional weight and thickness of the touch display panel, and may further reduce the light penetration rate, and increase reflectance and haze of the touch display panel.
On-cell and in-cell touch technology are invented to overcome the drawbacks of traditional touch technology described above. The on-cell technology is to dispose a touch sensor on a thin film and then bond the thin film onto the upper side of the upper glass substrate layer. The in-cell touch technology is provided to integrate the touch sensor within the display unit so that the display unit is provided with the ability of the touch panel. Therefore, the touch display panel does not need to be bonded with an additional touch panel so as to simplify the assembly procedure. Such skill is generally developed by display panel manufactures.
For the on-cell touch technology, it needs a sensing layer to be configured on an upper glass substrate or needs to use an upper substrate to increase touch sensing electrode, which not only increases the manufacturing cost but also complicates the manufacturing process, and which may also lower the aperture ratio and thus increase the manufacturing cost. Therefore, it desired for the aforementioned OLED touch display panel structure to be improved.